The present invention relates generally to a system and method for performing Time Difference Of Arrival (TDOA) and more specifically to a system and method for performing TDOA without requiring a common time base or clock calibration.
Time Difference Of Arrival (TDOA) refers to determining the position of a wireless transceiver (e.g. radio) by transmitting a signal from the wireless transceiver and then estimating the signal arrival time at multiple reference receivers, for example access points ‘APs’ in a Wireless Local Area Network (WLAN) system with known positions. The TDOA algorithm then compares the relative arrival time of the signal at the various APs to determine the radio's location. If the various APs do not share a common time base, clock calibration is required to determine the relative difference between the time bases of the APs. Performing clock calibration in practice is problematic for several reasons. First, it consumes time that could be used for data transmission. Second, the clock frequencies of the various APs will vary with time and therefore require periodic recalibration. Third, any inaccuracy in the clock frequency calibration will result in location estimation error.